This invention pertains to the field of battery chargers. More precisely, this invention enables a battery charger to provide automatically the current needed by a battery depending on its size.
A battery charger is a very convenient tool; it enables people to reuse their batteries and to be therefore able to use efficiently their preferred electronic devices. From the environmental point of view, a battery charger helps fight against the pollution by reducing the number of batteries required.
Preferably, a battery charger is intended to be as universal as possible, meaning that a user could decide to use the battery charger to charge a battery of any size from AAA-type to D-type. Unfortunately, batteries with different sizes have different charging current needs. A large battery such as a D-type battery will require more current than an AA-type battery or AAA-type battery. Detecting automatically the size of a battery inserted in the battery charger is highly desirable in order to provide a suitable current.
Various battery chargers have been disclosed in the past; for instance U.S. Pat. No. 5,543,702 discloses an alkaline battery charging method and a battery charger.
In the ""702 patent, the battery size detection is made by a slide with a V-shape fitting against the radius of curvature of the battery""s case, and moving out radially. The movement closes a series of three different switches. When an AAA-type battery is inserted or when no battery is inserted, no switch is closed. When an AA-type battery is inserted, a first switch is closed. A second switch is further closed when a C-type battery is inserted and a third switch is further closed when a D-type battery is inserted. These switches are used to vary the amount of resistance in the emitter leg of an emitter follower constant current charging source, causing the current to increase with decreasing resistance. The disclosed charger achieves the goal of providing automatically a current that depends on the physical size of the battery, however the radial motion of a V-shaped slide is extremely difficult to implement when the available space is limited. Furthermore, the charger in the ""702 patent requires a steady member for electrical contact with each battery and the V-shape slide. Both construction of the charger and use are somewhat complicated. There is therefore a need for detecting automatically the size of a battery that will overcome the above-mentioned drawbacks.
It is an object of the invention to provide a method and apparatus to recharge batteries of various sizes, such as AAA, AA, C and D.
It is an object to provide a battery charger that makes battery positioning with respect to terminal contacts easier and more secure.
According to one object of the invention, there is provided a battery charger receiving at least one battery horizontally on a support surface and having at least one switch detecting a variable battery size and a charging circuit responsive to said at least one switch, characterized in that said switch comprises a first pair of depressible posts, the first pair of depressible posts biased with respect to the support surface of the battery charger, said posts being spaced to guide the battery therebetween to be centrally positioned on the support surface and be depressed depending on a size of the battery.